Abstract
When we fixate small visual objects, incessant fixational eye movements translate tens to hundreds of foveal photoreceptors across the retinal image. Perhaps counter intuition, this constant visual jitter does not harm visual performance but in fact improves resolution. With simultaneous adaptive optics foveal cone-resolved imaging and micro-psychophysics, we here studied the direct relationship between visual resolution, photoreceptor topography in the central fovea, and fixational drift in a number of healthy eyes. Across subjects, we find that visual resolution was mainly governed by the photoreceptor sampling capacity of the individual eye. Resolution was highly correlated between fellow eyes, with the dominant eye performing better. When ocular aberrations were removed, resolution acuity was below the Nyquist sampling limit in all eyes, an effect that can in part be attributed to the spatiotemporal information produced by drift. We found that fixational drift showed a directional component that optimized retinal sampling from lower to higher cone density areas, an observation challenging the view that drift is primarily a result of random motor jitter.